Thermal receptacle with phase change material

ABSTRACT

A liquid receptacle for rapidly lowering the temperature of a liquid contained therein to a warm range suitable for human contact and maintaining the liquid in the warm range for an extended period of time includes an inner vessel with an open upper end and a closed lower end and a wall connecting the upper and lower end. An insulated outer shell is spaced from the inner vessel to define an interstitial chamber between the inner vessel and the outer shell. A phase change material occupies the chamber and regeneratively absorbs thermal energy from the liquid to cool the liquid and then releases the thermal energy back to the liquid to maintain the temperature of the liquid.

RELATED APPLICATION

[0001] This patent application claims priority from provisional patentapplication Serial No; 60/043,431 filed Apr. 7, 1997 entitled “ThermalReceptacle with Phase Change Material.”

TECHNICAL FIELD

[0002] The subject invention relates generally to liquid receptacles orcontainers and more specifically to a receptacle that rapidly cools ahot liquid to a warm range and then maintains the fluid in the warmrange for an extended period.

BACKGROUND OF THE INVENTION

[0003] There have been many attempts in the past to maintain liquids andsolids within certain temperature ranges. Hot beverages are usuallyprepared and served at temperatures well above the temperature at whichconsumers prefer to drink them. Typically, the consumer must wait anextended period for the beverage to sufficiently cool before drinkingit. Some impatient consumers will attempt to drink the beverage too soonresulting in burns to the mouth. Similarly, if the drink is spilledbefore it has had sufficient time to cool, burns to the skin may result.Therefore, it is desirable to rapidly cool the beverage from thetemperature at which it is served to an acceptable drinking range. Oncethe beverage is within the acceptable drinking temperature range, it isdesirable to maintain the temperature of the beverage within this rangefor an extended period of time.

[0004] Many approaches have been tried for both rapidly cooling a hotbeverage and for maintaining the temperature of the beverage within anacceptable drinking temperature range. To rapidly cool a hot beverage,ice or a cool liquid (e.g., water or milk) can be added to the hotbeverage. This approach rapidly cools the beverage but dilutes the hotbeverage. This is frequently undesirable. This approach is ofteninconvenient and imprecise; if the person adds too little or too much,the temperature of the hot beverage will be higher or lower than desiredand may require further attention. Finally, this approach does notprovide any assistance in maintaining the temperature of the hotbeverage in the acceptable drinking temperature range. Once the beveragereaches an acceptable temperature, it will continue to lose thermalenergy to its surroundings. This results in the beverage becoming cooltoo quickly. Therefore, the beverage remains within an acceptabledrinking temperature range for only a short period.

[0005] A hot beverage can also be cooled by pouring it into a coolcontainer. Thermal energy is transferred from the hot beverage to thecool container thereby warming the container and cooling the beverage.This approach suffers from some of the same limitations as adding coolliquid or ice. If the cup is too cool or too warm or has too much or toolittle thermal mass, the beverage will stabilize at the wrongtemperature. Also, while a heavy container will slow the rate of coolingsomewhat due to the increase in the total thermal mass of the system,the effect will be small and the beverage will only remain in the idealdrinking range for a short period.

[0006] Up to this time, the primary method employed for slowing thecooling rate of a beverage was to insulate the container. Everythingfrom simple foam cups to expensive and sophisticated vacuum mugs isused. These approaches slow the cooling rate of the beverage. However,the ability of the insulated mugs currently on the market to maintainbeverage temperatures is relatively limited. Even the best mugs usuallykeep liquids warm for less than 45 minutes. Stainless, vacuum insulatedmugs are best at maintaining temperature, but no product currentlyexists which can passively cool a hot beverage quickly. Also, thebeverage in an insulated container will continue to cool despite theinsulation. The cooling rate will only be slowed. Insulation does notprovide a way to add thermal energy back to the beverage.

[0007] To maintain the temperature of a beverage as it cools, the priorart has taught the use of an electric heater. At least one manufacturerproduces a portable refrigerator/heater which plugs into a car'scigarette lighter and may be used to cool or warm beverages. Likewise,plug-in mugs, hot plates and immersion devices may be used to keepbeverages warm. Some beverage containers are available that plug intoaccessory plugs in automobiles. A container may also be periodicallymicrowaved to reheat the contents. All of theses approaches suffer fromlack of portability and dependence on outside energy sources. They alsofail to address the need to rapidly cool a beverage to an acceptabledrinking temperature range.

[0008] The demand for hot beverages is very high, especially for coffeeand tea, the most popular adult hot beverages. In 1990, approximately42% of the US population consumed coffee and 30% consumed tea. Thenumber of occasions that hot beverages are consumed away from home hasincreased significantly in recent years. By 1999, the Specialty CoffeeAssociation of America predicts that there will be approximately 10,000coffee cafes in comparison to the approximately 3,000 in 1996. TheAssociation forecasts that of the $1.5 billion in sales coffee cafeswill ring up in 1999, 20% will be from hot beverage take out.

[0009] Therefore, it is desirable to develop a reusable beveragecontainer that will rapidly cool a beverage to an acceptable drinkingtemperature, will maintain the temperature within an acceptabletemperature range for an extended period, requires neither manipulationby the consumer or the input of external energy, and is portable.

[0010] Another related application requiring temperature regulation isbaby bottles. Beverages given to infants usually must be warmed but itis important to not give an infant a beverage that is too hot. Infantscannot tolerate temperatures as high as adults and parents must learn todetermine the maximum acceptable temperature for their child. Therefore,when a beverage is warmed for an infant, it may be necessary to cool itrapidly back to an acceptable temperature. If the beverage is too warm,a parent typically must add cool liquid or allow time to pass. Also, ifthe infant is fussy and does not drink the entire contents of the bottleimmediately, the contents may cool to the point that the infant will notdrink it. Then the parent must reheat the bottle being careful to notoverheat it. Insulated baby bottles are available which extend the timethe contents are acceptably warm but they fail to add thermal energyback to the bottle contents. Therefore, it is desirable to develop ababy bottle that will rapidly reduce the temperature of a beverage to asafe drinking temperature for an infant and then will maintain thattemperature for an extended period.

[0011] Another application where it is desirable to regulate thetemperature of a liquid is in bathing tubs. When a person takes a bathor soaks in a tub, the water must be within a certain range to becomfortable. If the water is too hot, the person may be unable to enterthe water or may be injured by it. This is especially important withinfants and small children. If the water is too hot, cold water must beadded until the temperature falls in an acceptable range. Once the wateris at an acceptable temperature, it is desirable to maintain itstemperature for the period of the bath. If a person wishes to soak or achild wishes to play in the tub for a period of time, the water maybecome uncomfortable due to its falling temperature. Then, additionalhot water must be added to raise the temperature back into theacceptable range. Insulated bathing tubs are available which help reducethe rate of temperature loss but do not address the issue of water thatis too hot. They also fail to add thermal energy back into the tub. Somewhirlpool tubs include heaters for maintaining the temperature of thewater but these devices are expensive to purchase and operate, require acomplex system of pumps, valves and switches, and are noisy inoperation. They also fail to address the issue of water that is too hot.Therefore, it is desirable to develop a bathing tub that would rapidlyreduce the temperature of water to an acceptable bathing range and thento maintain the temperature of the water within the acceptable range foran extended period.

SUMMARY OF THE INVENTION

[0012] This invention addresses the need to rapidly lower thetemperature of a liquid to a warm range suitable for human contact andthen maintain the liquid in the warm range for an extended period oftime. The invention comprises a liquid receptacle having a side wallwith a lower end and an open upper end. A bottom wall closes off thelower end of the side wall. The side wall has an inner surface and aspaced outer surface. An interstitial chamber is defined by the spacebetween the inner and outer surfaces. An insulation layer is disposed atleast partially between the chamber and the outer surface of thereceptacle. A phase change material at least partially fills thechamber. The phase change material regeneratively absorbs thermal energyfrom a hot liquid in the receptacle thereby rapidly lowering thetemperature of the liquid and then the material releases the thermalenergy back to the liquid to maintain the temperature of the liquid.

[0013] The present invention is suitable for any application requiringthe rapid lowering of the temperature of a liquid in a container andthen the maintenance of the temperature of the liquid for an extendedperiod of time. Among other things, the invention can be applied todrinking mugs or cups, baby bottles, carafes, and bathing tubs.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014]FIG. 1 is a cross sectional view of a drinking receptacleaccording to the present invention.

[0015]FIG. 2 is a graph depicting the temperature of a liquid in thesubject drinking receptacle versus time, and showing for comparisonpurposes the heat loss characteristics of a baseline prior art drinkingreceptacle.

[0016]FIG. 3 is a cross sectional view a foam insulated plastic outershell for the subject drinking receptacle.

[0017]FIG. 4 is a cross sectional view as in FIG. 3 but showing analternative vacuum insulated stainless steel outer shell for the subjectdrinking receptacle.

[0018]FIG. 5 is a cross sectional view of a baby bottle which is a firstalternative embodiment of the present invention.

[0019]FIG. 6 is a cross sectional view of a carafe which is a secondalternative embodiment of the present invention.

[0020]FIG. 7 is a cross sectional view of a bathing or soaking tub whichis a third alternative embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0021] Referring to the Figures, wherein like numerals indicate like orcorresponding parts throughout the several views, a liquid receptacle isgenerally indicated at 10. The receptacle 10 includes a inner vessel 12with an open upper end 13 and a closed lower end 14 and a wall 16connecting the upper 13 and lower 14 ends. An insulated outer shell 18is spaced from the inner vessel 12 defining an interstitial chamber 20therebetween. Phase change material is disposed within the chamber 20.

[0022] Preferably, the inner vessel 12 is either wholly or partiallyformed of a material having a high thermal conductivity such asaluminum, copper or alloys thereof. Pure aluminum has a thermalconductivity of 237 Watts/meter-degree Kelvin when measured at 300degrees Kelvin. Most aluminum alloys have a thermal conductivity above150 Watts/meter-degree Kelvin. Pure copper has a thermal conductivity of401 Watts/meter-degree Kelvin. Most alloys of copper have thermalconductivities significantly lower than pure copper. It is mostpreferred that inner vessel be formed from a material having a thermalconductivity above 150 Watts/meter-degree Kelvin. As should be obviousto one skilled in the art, other materials, including gold and silver,meet this requirement. A material with a lower thermal conductivity mayalso be used but the performance of the invention will be reducedaccordingly. The inner vessel 12 may be coated, anodized, or plated inorder to improve the appearance, resistance to oxidation, orcleanability of the vessel 12. Alternatively, the vessel 12 may beformed from 2 or more different materials. The closed lower end 14 couldbe formed from plastic while the wall 16 is formed from coated aluminum.A two material inner vessel 12 may be beneficial for cost,manufacturing, or appearance reasons.

[0023] One embodiment of the thermal receptacle 10 has an upper rimoutside diameter 24 of about 3.5″, and a bottom outside diameter 26 ofabout 2.75″. The bottom diameter 26 is small enough for the receptacle10 to fit into typical vehicle drink holders. Total wall thickness 28varies from a maximum of about ⅝″ to a minimum of about ⅜″ at theuppermost portion. The receptacle 10 may include a removable lid whichselectively closes off the upper end 13 of the inner vessel 12.Alternatively, the lid could sit higher and close off the top of thethermal receptacle 10. The receptacle 10 also includes a plasticremovable handle 29. The handle 29 can be removed allowing use of thereceptacle 10 in vehicle drink holders.

[0024] To use the receptacle 10, a consumer removes the lid and pours ahot beverage or liquid into the inner vessel 12 of the receptacle 10,which is initially at room temperature. Because the inner vessel 12 isformed of a thermally conductive material, the chamber 20 is inthermally conductive communication with the beverage or liquid in theinner vessel 12. The thermally conductive material of the inner vessel12 begins conducting the thermal energy of the hot beverage or liquidinto the chamber 20 where it is absorbed by the phase change material.As the phase change material absorbs the thermal energy, the temperatureof the phase change material rises from room temperature to its phasechange temperature. Preferably the phase change material will changephases in the range of 110-160 degrees Fahrenheit (the phase changetemperature). Most preferably, the phase change temperature will be inthe range of 140-155 degrees Fahrenheit if the receptacle is to be usedby adults. Preferably, the phase change will be from solid to liquid; amelting. One acceptable phase change material is palmitic acid. Manyother phase change materials are also available with acceptable phasechange temperatures. One class of phase change materials includes a setof naturally occurring fatty acids (soaps) with melting points in therange of 110° F. to 160° F. These materials are advantageous due totheir non-toxic and relatively innocuous characteristics. Theperformance of these materials is enhanced if they are of relativelyhigh purity (95% or better). Examples are stearic, palmitic, andmyristic acids. Other possibilities for the phase change materialinclude heavy alcohols, such as cetyl alcohol. As will be clear to oneof skill in the art, many materials are available which can be used asphase change materials. However, to be useful for thermal management, amaterial must change phases at a temperature close to the temperaturerange desired to be maintained. Also, it is desirable that the materialbe non-toxic and be readily available at a reasonable price.

[0025] Once the phase change material reaches its melting point, thetemperature of the phase change material will no longer rise as thethermal energy is absorbed causing the material to melt (change phases).As the phase change material absorbs thermal energy from the hotbeverage, the temperature of the hot beverage will fall. The temperatureof the hot beverage will continue to fall until the beverage and thephase change material are in thermal equilibrium; e.g., they are at thesame temperature. The quantity of the phase change material is chosen sothat during its phase change it can absorb enough thermal energy to coolthe hot beverage from the boiling point of water down to within a warmrange acceptable for human consumption. Once the hot beverage is cooledto within the warm range, the beverage and the phase change material areat equilibrium and the beverage is drinkable. As the beverage losesthermal energy to the surrounding atmosphere, its temperature will beginto fall below the phase change temperature of the phase change material.At this point, the phase change material will begin to transfer thermalenergy back through the inner vessel 12 into the beverage. This thermalenergy will maintain the temperature of the hot beverage near the phasechange temperature of the phase change material as the phase changematerial resolidifies. Once the phase change material converts back tothe solid phase, its temperature will begin to fall and the beveragetemperature will no longer be maintained. Because the phase changematerial remains at the phase change temperature during the phasechange, the beverage will be maintained near the phase changetemperature for an extended period.

[0026] The warm range acceptable for human contact or consumption variesdepending on the application. For adults, the warm range acceptable forconsumption of a hot beverage is approximately 120 degrees Fahrenheit toapproximately 154 degrees Fahrenheit. Above 154 degrees, hot beveragesare too hot for most consumers. Most consumers prefer to start drinkinga hot beverage at around 145 degrees Fahrenheit. Below 120 degrees, mostconsumers find that a beverage has become too cool to be palatable.Obviously, preferences vary so receptacles 10 can be manufactured with avariety of phase change materials to tailor the warm range achieved.Also, a receptacle designed for children's beverages requires a lowerwarm range and therefore a phase change material with a lower phasechange temperature is most desirable.

[0027] Referring now to FIG. 2, the thermal characteristics of thereceptacle 10 adapted for hot beverages for adults are shown. A seriesof datapoints labeled as baseline indicate the temperature of a hotbeverage poured into a typical prior art plastic coffee mug. Thetemperature of the beverage falls slowly but steadily to the upper limitof the warm range (labeled as Drinking Temperature Range) acceptable forhuman consumption, which in this example is approximately 150° F. Thetemperature of the beverage continues to fall at approximately the samerate until it falls below the lower limit of the warm range which inthis example is approximately 120° F. Consequently, the beverage is onlywithin the warm range or acceptable drinking temperature range for ashort period of time.

[0028] The series of datapoints labeled as “Phase Change Mug” illustratethe thermal characteristics of a receptacle constructed according to thepresent invention. The datapoints indicate the temperature of a hotbeverage poured into the receptacle versus time. The beverage cools veryrapidly as the thermal energy of the beverage is absorbed by the phasechange material. The beverage rapidly falls to the upper limit of thewarm range and then the cooling rate slows. The beverage remains withinthe warm range for an extended period; more than an hour.

[0029] Referring now to FIGS. 3 and 4, the outer shell is showngenerally at 18. The shell 18 has an inner surface 30, an outer surface32, and an upper edge 34 that terminates in a lip 36 for drinking fromthe receptacle. Two embodiments of the outer shell 18 are envisioned. Inthe preferred embodiment, shown in FIG. 3, the outer shell 18 has arigid plastic outer surface 32 and a insulating foam layer 38. The outersurface 32 defines the outer contours of the receptacle 10. The innersurface 30 of the outer shell 18 is defined by the inner surface of theinsulating foam layer 38. The insulating foam layer 38 can be made of avariety of insulating foams. Two acceptable foams are polyurethane foamand polystyrene foam.

[0030] A first alternative embodiment of the outer shell 18, as shown inFIG. 4, consists of a stainless steel outer surface 32 and inner surface30 that form a totally sealed chamber 40. The chamber 40 is evacuatedthereby creating a vacuum insulated outer shell 18. The two versions ofthe outer shell 18 have similar shapes but the stainless version issomewhat heavier and more costly to produce. A plastic insulated versionof the complete receptacle assembly with a capacity of about 12 fluidounces has a dry weight of about 12 oz. and the stainless version has adry weight of about 16 oz.

[0031] The performance of the receptacle is greatly enhanced by theinsulated outer shell 18. The insulation slows the loss of thermalenergy from the phase change material thereby greatly extending theperiod that the beverage can be maintained within the warm range.

[0032] Referring back to FIG. 1, an additional feature of the presentinvention can be appreciated. The inner vessel 12 is recessed within theouter shell 18. The upper end 13 of the inner vessel 12 is located belowthe lip 36 of the outer shell 18. This prevents the lips of a consumerfrom contacting the inner vessel 12 when the consumer drinks from thereceptacle 10. Because the inner vessel 12 is highly thermallyconductive, the upper end 13 can be uncomfortably warm and therefore itmost preferred that it is positioned so that it does not contact theconsumer's lips. The amount that the upper end 13 should be recessedvaries depending on the shape of the lip 36 and the overall design ofthe receptacle 10. With the shape illustrated in FIG. 1, it is preferredthat the upper end 13 be spaced from the lip 36 by at least {fraction(1/8)} inch and more preferably by at least {fraction (1/4)} inch. Theupper end 13 of the inner vessel 12 seals to the inner surface 30 of theouter shell 18. The seal between the upper end 13 and the inner surface30 must be sufficient to reliably retain the phase change material inchamber 20. Several sealing methods are available. Currently, it ispreferred to form the inner surface 30 with a small recess 37 for theupper end 13 of the inner vessel 12 to snap into. A silicon sealant isapplied to the recess 37 before the inner vessel 12 is inserted. Apreformed silicon seal offers an alternative. It can be formed to fill aportion of the recess 37.

[0033] A baby bottle 110 incorporating a phase change material is afirst alternative embodiment of the present invention as shown in FIG.5. The baby bottle 110 includes a thermally conductive inner vessel 112surrounded by an insulated outer shell 118. The outer shell 118 isspaced from the inner vessel 112 so as to form a chamber 120 which is atleast partially filled with a phase change material. The acceptabletemperature for liquid consumed by infants is significantly lower thanthe temperature desired by adults so a phase change material with alower phase change temperature is used. The outer shell 118 can beplastic with a foam insulation layer or vacuum insulated stainlesssteel. It is desirable to minimize the weight of a baby bottle to allowan infant to support its weight unaided. Therefore, a lightweightplastic outer shell 118 with foam insulation is most preferred. Theshell 118 may also incorporate a handle or other gripping means to allowan infant to more easily grasp the baby bottle 110. For maximum benefitfrom the phase change material, the infant beverage should be added tothe bottle at a temperature above the warm range for infants so thatexcess thermal energy is absorbed by the phase change material. After ashort period, the phase change material will have absorbed the excessthermal energy thus lowering the temperature of the beverage into thewarm range for an infant. The excess thermal energy will serve tomaintain the temperature of the beverage for an extended period. This isdesirable if the infant is fussy and refuses to drink the entirecontents of the bottle immediately. The temperature stabilizing effectof the phase change material has the additional benefit that parentswill not have to worry about checking to see if the beverage is too hot.The bottle holds sufficient phase change material that a beverage couldbe added at boiling temperature. The bottle will cool the beverage tothe acceptable range within a short period. Therefore, parents can beconfident that as long as they wait a proscribed period, the beveragewill be safe. The bottle may also incorporate a timing device or atemperature indicator to provide the parents with additionalinformation.

[0034] In FIG. 6, a second alternative embodiment, a carafeincorporating phase change material, is generally shown at 210. Thecarafe 210 includes a thermally conductive inner vessel 212 surroundedby an insulated outer shell 218. The shell 218 is spaced from the innervessel 212 so as to form a chamber 220 which is at least partiallyfilled with a phase change material. Since the carafe 210 will be usedto hold hot beverages for pouring into mugs or cups, it is desirable tohold the beverage at a higher temperature than the maximum acceptabledrinking temperature. When the beverage is poured from the carafe 210into a mug, the mug will cool the beverage. Therefore, the pouringtemperature should be higher than the desired drinking temperature. Thecarafe 210 will differ from the drinking receptacle 10 in that thecarafe 210 will require significantly more phase change material toadequately absorb and store the thermal energy of the increased mass ofhot beverage. Also, a phase change material with a higher phase changetemperature is preferred.

[0035] In FIG. 7, a third alternative embodiment, a bathtubincorporating phase change material, is generally shown at 310. Thebathtub 310 includes a thermally conductive vessel 312. Attached to theexterior of the vessel 312 are boxes 313, 314, 316 which are at leastpartially filled with phase change material. Surrounding the boxes 313,314, 316 are insulating layers 318, 320, 322. When hot bathing water isadded to the bathtub 310, the phase change material absorbs thermalenergy conducted into the boxes 313, 314, 316 from the bathing water.The bathing water quickly cools to an acceptable bathing temperature andthen the phase change material starts conducting thermal energy backinto the bathing water thereby maintaining its temperature. The boxes313, 314, 316 are removably attached to the exterior of the vessel 312so that boxes with different phase change materials can be substituted.This allows for changes in the sustained temperature of the bathingwater as may be desirable when adults and children use the same bathtub.For example, when someone plans to use the tub, they would check to seewhat boxes 313, 314, 316 are connected. If a child is going to use thetub, the low temperature version of the boxes 313, 314, 316 should beconnected. After confirming that the low temperature boxes areconnected, an adult can fill the tub with hot water for the child. Aftera set period of time has passed, the temperature of the water in the tubwill be acceptable and safe for the child. If later, the adult wishes touse the same tub for a higher temperature soak, they would change theboxes 313, 314, 316 to the higher temperature version, drain the tub ifnecessary, and refill the tub with hot water. It should be noted thatthe tub would require refilling with hot water if the boxes 313, 314,316 were changed. The new hot water would then melt the phase changematerial in the new boxes 313, 314, 316 for the new bath. If the boxes313, 314, 316 were changed without changing the water in the tub, thewater in the tub would not have sufficient thermal energy to melt thephase change material in the boxes 313, 314, 316. Therefore, the phasechange material could not provide the temperature maintenance functionthat it would ordinarily provide if it were melted by the excess thermalenergy of fresh hot water.

Manufacturing of the Mug

[0036] The current design for the plastic version of the receptacle 10shown in FIG. 1 calls for four parts which require expensive productionequipment, three of which are injection molded, and one of which is astamped aluminum part. The injection molded parts include the outershell 18 of the receptacle, the handle 29, and an insulating lid. Thestamped part is the aluminum inner vessel 12. Once these parts areproduced, the remaining assembly can be done in a light manufacturingfacility. The receptacle 10 is assembled in a series of fourworkstations, labeled as receiving, foam insulation injection, generalassembly, and finally, packaging and shipping. At the insulationinjection workstation, a plastic outer shell is snapped on to an innermold and a portioned amount of urethane foam is injected into the cavityproduced between the outer shell 18 and the inner mold. After thisprocess is completed, the assembly is set aside to cure, generally in aheated area and for a period of two to three hours.

[0037] The general assembly station receives warmed, foam lined plasticouter shells 18 from the foaming station, adds the liquid phase changematerial, applies a bead of adhesive to the sealing point, and snaps thealuminum inner vessel inside the shell 18. This assembly operation mustbe performed “hot,” that is, at a temperature that exceeds that of themelting point of the phase change material. This assembly temperaturevaries, but generally does not exceed 150° F. The handle 29 and lid arealso added at this station to complete the assembly.

[0038] Alternative manufacturing technologies include the use of newexpandable polymers such as expandable polypropylene. The use of thesematerials in producing plastic versions of the receptacle may reduce thefixed costs of injection molds and injection molding machines, as theywill only require blow molds and stream blowing machines. These latterdevices are approximately {fraction (1/4)} the cost of the injectionmolding equipment.

[0039] The manufacture of this stainless vacuum insulated version of thereceptacle 10 varies only in the construction of the outer shell 18. Thestainless outer shell 18 is composed of two pieces of stamped stainlesssteel. One different workstation is required for the fabrication of thevacuum jacketed stainless outer shell 18 from the stamped parts. Thisworkstation is referred to as the welding and evacuation station, and inthe four workstation sequence, it replaces the foaming station. As aresult, the station sequence for the stainless versions is: receiving,welding and evacuation, assembly, and packaging.

[0040] The stainless steel version of the receptacle 10 requires twoadditional stampings, described as an inner and an outer half. Theassembly of the stainless steel outer shell 18 includes pressing theinner and outer halves of this shell together. This operation leaves aseam at the top of the shell 18, and this seam is sealed by a TIGwelding process, accomplished with the parts in a rotating holding jig.

[0041] Following the welding of the upper edge 34, the shell 18 isinverted, and a small tube attached by welding to the center of adepression in the bottom of the shell 18. This tube serves as theevacuation port. The small tube is connected to a vacuum source in adifferent section of the workstation, and left to evacuate. Once asufficient vacuum has been reached, the shell 18 is leak checked. If theshell 18 passes this leak check, the evacuation tube, still under activepumping, is crimped, then welded off. Shells that fail the vacuum checkmust be inspected and their tops rewelded.

I claim:
 1. A liquid receptacle for rapidly lowering the temperature ofa liquid contained therein to a warm range suitable for human contactand maintaining the liquid in the warm range for an extended period oftime, said receptacle comprising: an inner vessel having an open upperend and closed lower end and a wall connecting said upper end and saidlower end; an insulated outer shell spaced from said inner vesseldefining an interstitial chamber therebetween; and a phase changematerial disposed within said chamber for regeneratively absorbingthermal energy from the liquid and then releasing the thermal energy tothe liquid to maintain the temperature of the liquid.
 2. A receptacleaccording to claim 1 wherein said outer shell has an inner surface andan outer surface; and said upper end of said inner vessel is in sealingengagement with said inner surface of said outer wall.
 3. A receptacleaccording to claim 1 wherein said inner vessel is formed from a materialhaving a thermal conductivity greater than 150 Watts/meter-degreeKelvin.
 4. A receptacle according to claim 3 wherein said material isselected from the group consisting of aluminum, aluminum alloys, copper,and copper alloys.
 5. A receptacle according to claim 1 wherein saidouter shell comprises an inner layer and an outer layer with anevacuated void therebetween for vacuum insulating said outer shell.
 6. Areceptacle according to claim 1 wherein said outer shell comprises alayer of insulating foam.
 7. A receptacle according to claim 6 whereinsaid foam is selected from a group consisting of polyurethane andpolystyrene.
 8. A receptacle according to claim 1 wherein said outershell is plastic.
 9. A receptacle according to claim 1 wherein saidouter shell is stainless steel.
 10. A receptacle according to claim 1wherein said phase change material has a solid to liquid phase changetemperature within the range of 110 degrees Fahrenheit to 160 degreesFahrenheit.
 11. A receptacle according to claim 10 wherein said phasechange material is selected from the group consisting of naturallyoccurring fatty acids.
 12. A receptacle according to claim 1 whereinsaid phase change material is palmitic acid.
 13. A receptacle accordingto claim 1 wherein said receptacle is a mug for receiving a hotbeverage.
 14. A receptacle according to claim 1 wherein said receptacleis a baby bottle.
 15. A receptacle according to claim 1 wherein saidreceptacle is a carafe.
 16. A receptacle according to claim 1 whereinsaid receptacle is a bath tub.
 17. A liquid receptacle for rapidlylowering the temperature of a hot beverage contained therein to a warmrange suitable for human consumption and maintaining the liquid in thewarm range for an extended period of time, said receptacle comprising:an inner vessel having an open upper end and closed lower end and a wallconnecting said upper end and said lower end; an insulated outer shellspaced from said inner vessel defining an interstitial chambertherebetween; said outer shell having an inner surface and an outersurface and an upper edge terminating in a lip for drinking; said upperend of said inner vessel being in sealing engagement with said innersurface of said outer shell and spaced from said lip for preventingcontact between said inner vessel and the mouth of a consumer of liquidfrom said receptacle; and a phase change material disposed within saidchamber for regeneratively absorbing thermal energy from the beverageand then releasing the thermal energy to the beverage to maintain thetemperature of the liquid.
 18. A receptacle according to claim 17wherein said upper end of said inner vessel is spaced from said lip by adistance greater than 0.125 inches.
 19. A receptacle for bathingcomprising: an inner vessel having an inner surface and an outersurface; a container contacting said outer surface and in thermallyconductive communication with said inner surface; and phase changematerial disposed within said container.
 20. A receptacle according toclaim 19 wherein said container is insulated for preventing heat loss tothe atmosphere.
 21. A receptacle according to claim 19 wherein saidcontainer is removably attached to said outer surface for removal andreplacement of said container.
 22. A method of rapidly cooling a hotliquid to a temperature within a warm range suitable for human contactand maintaining the liquid in the warm range for an extended period oftime comprising the steps of: a) conducting thermal energy from the hotliquid through a thermally conductive layer and into a chambercontaining a phase change material; b) absorbing the thermal energy intothe phase change material thereby converting the phase change materialfrom a solid state to a liquid state until the liquid and the phasechange material are substantially at equilibrium; and c) releasingthermal energy from the phase change material and conducting the thermalenergy into the liquid thereby supporting the temperature of the liquidand converting the phase change material from the liquid state to thesolid state.
 23. A method of making a liquid receptacle comprising thesteps of: a) molding a plastic outer shell; b) stamping an innerreceptacle from a material selected from a group comprising aluminum,aluminum alloys, copper, and copper alloys; c) injecting uncured liquidfoam into the outer shell; d) inserting a die into the outer shellthereby forming the foam into a layer between the outer shell and thedie; e) allowing the liquid foam to cure into a solid foam creating afoam lined outer shell; f) removing the die; g) melting a phase changematerial by raising the temperature of the material above the solid toliquid phase change temperature; h) injecting the phase change materialinto the foam lined outer shell; i) inserting the inner receptacle intothe outer shell so that the receptacle is sealed to the outer shell andthe inner receptacle is spaced from the outer shell defining aninterstitial chamber containing the phase change material.